COMMISSION E: Electromagnetic Noise and Interfere (November 2004 – October 2007)
Edited by Ryuji KOGA
Anthropogenic EM Noise and EMC
E.1 2009 International Symposium
on EMC, Kyoto
EMC'09/Kyoto is organized
by Prof. R. Koga, Okayama University,
and will be held
be held in Kyoto
at Kyoto International Conference Center,
from June
20th to 24th, 2009. This is the sixth EMC Symposium
in Japan,
because
they have
been held
every
five years
since
1984. More
than 650 people
are expected
to attend
from 20 countries including
Japan,
and about
250 technical
papers
will be presented
at the Symposium.
E.2
EMC measurement technology
The studies of EMI antenna
and electromagnetic
field probe calibration
method,
electromagnetic
field probe using electro-optical
crystal,
EMI suppression
effect by ferrite core,
measurement method
of lightning
surge,
evaluation method
of RF absorber
reflectivity
in millimeter
wavelength,
etc, have been
performed
in this period.
Detail
descriptions
are presented
below.
E2-1. Magnetic
field probe using magnet-impedance effect
A high frequency
carrier
type magnetic
field probe, which
has high sensitivity and high
resolution,
called GMI (giant magneto-impedance) probe is proposed [Tan,
et al., 2005, 2006a, 2006b; Kayano,
et al., 2006]. And its validity of magnetic
near field
measurements is demonstrated by comparing
with a conventional
shielded
loop coil
probe
and numerical
modeling.
The GMI probe
can clearly
detect current concentration
at an edge of a microstrip line, which allows
high resolution measurements.
E2-2
Antenna
factor
of EMI measuring
antennas
Radio disturbances emitted
from electronic
equipment have
been measured
with an EMI antenna,
where
the disturbance level
is expressed
in terms of the electrical
field strength. In practical
measurements, it is given by multiplying
the received
voltage
by the antenna
factor
of a measuring
antenna
used. In order
to improve
the accuracy of the antenna
factors
in EMI measurement, new antenna
calibration methods
have been
developed:
(1) Application of the non-linear
least
squares
method
has been investigated to reduce
the uncertainty
due to the ground
reflection
for the conventional
EMI antenna
calibration in the frequency
range
from 30 MHz to 300 MHz [Fujii, et al., 2005a]. (2) An antenna
calibration technique was proposed using the Standard
Antenna
Method
for vertical polarization. Based on the results of theoretical
investigation, appropriate
antenna
arrangements were
found for the calibration
of a biconical
antenna
[Tsushima,
et al., 2005]. (3) A new calculable loop
antenna
having
a 180-degrees
hybrid junction was developed
to improve
the evaluation accuracy
of the generated
field strength for the Standard
Filed Method.
The antenna
is also applicable
to other
calibration methods,
such as Standard
Antenna
Method
and Three-Antenna
Method
[Fujii, et al., 2005b]. (4) A new measurement method
of a free space antenna
factor
was developed
using
a reverberation
chamber
[Harima
2005a, 2006, 2007a, 2007b]. (5) Methods for calibrating broadband EMI antennas
were investigated [Yamanaka,
2005]
E2-3
Calibration of electromagnetic
probe
In order to calibrate
an electromagnetic
probe
up to 18 GHz, a method using open-ended waveguides has been proposed
as the standard
radiators in the frequency
range
from 500 MHz to 18 GHz [Ishigami, et
al., 2002, 2003a]. A calibration facility was established
with an anechoic
chamber.
The uncertainty
of the facility
was evaluated
as }0.96 dB (500 MHz-8.2 GHz) and }1.14 dB (above 8.2 GHz) at the confidence
coefficient
of 95%, respectively.
A TEM cell is also
used for the calibration
below
500MHz. The uncertainty
of the facility
was evaluated
as }0.74 dB at a confidence coefficient
of 95%
E2-4 Measurements of EMI suppression
characteristics of ferrite cores
A major source of the electromagnetic
interference in the frequency
range
below
1000 MHz is disturbance currents flowing on the cables connected
to an electronic
device.
In order to reduce
the noise
currents,
ferrite
cores are usually attached
to encircle
the cables.
However,
there
is no standard
method
for measuring
the EMI suppression
characteristics of the core.
Hence,
a measurement method
for the insertion
loss and the reflection
coefficients
of a ferrite
core has been
studied
and developed
[Urabe, et al., 2006a, 2006b].
E. 3
Printed
circuit
board
(PCB) and chip level
EMC
EMI control
technologies
are still
of prime
interest
of high-speed electronic
device
supplier.
Engineers
who design
electronic
apparatuses
are always
more effective, more
versatile method
of EMI control.
Research
activities
are held in many
farms, but results are apt to be closed
to the farm. EMC researches
are held in a few universities out of more
than 100 Universities that have engineering
department.
The studies of simulation
of undesired noise form
PCB, EMI simulation, EMC design, EMC modeling,
Design
tools, etc, have
been performed in this
period.
Detail
descriptions
are presented
below.
E3-1 Conducted noise currents from
PCB
Conductive noise currents flowing out from vehicle-mounted electronic
equipment composed
of multi-layer printed circuit boards (PCBs)
to wire-harnesses form
a major
disturbance source for vehicle
mounted
radios.
By using
actual
vehicle-mounted electronic
equipment, it was shown that,
to reduce
the noise
current
outflow
of this type,
combining,
not separating, the ground layer patterns
of a digital
circuit
and an analog
circuit
is more advantageous,
while the mechanism
remains
unknown.
Based
on an idea that
this mechanism
generates
from a change
in the amount
of common-mode return
currents
flowing
to the ground,
noise
current
outflows
were simulated
with the method
of moment
from three types
of simple
PCBs having
different
ground
patterns,
which were
validated
from measurement of scattering
parameters.
Furthermore, it was confirmed
that slits
on a ground
pattern
allow
conductive
noise
currents
to flow out from
PCBs [Maeno, et al., 2006]
Electromagnetic disturbances for vehicle-mounted radios can be caused by conducted noise currents that flow out from electronic
equipment for vehicles
to wire-harnesses. For reducing the conducted noise currents from
electronic
equipment for vehicles,
a simulation
and an experiment were
made on how ground patterns
affect the noise currents from
three-layer printed circuit boards (PCBs) with slit-types and plane-type ground
patterns.
As a result,
it was shown
that slits
on a ground
pattern
allow
conducted
noise
currents
to flow out from
PCBs to wire-harnesses. For the PCBs with plane-type ground
and one of three
slit-type
patterns,
on the other
hand, both
the simulation
and examination
showed that
resonance
phenomena
occur at unexpected
low-frequencies.
A circuit
analysis
revealed
that the above phenomena
can be caused
by the imbalance
of a bridge
circuit
consisting
of the trace
circuits
on the PCB [Maeno, et al., 2007a].
Using actual PCBs in electronic
equipment for vehicles,
Maeno, et al. investigated whether the grounds of digital and analogue
circuits
should
be combined
or separated to reduce
the conductive
noise
current
from wire-harness connected
to the PCBs. As a result,
it was shown
that, in the FM radio frequency
band, a ground without separation
gives less
noise
currents
and radiated
emissions
[Maeno, et al., 2007b].
E3-2
Simulation
of undesired noise from
PCB
In order to explain
the undesired electromagnetic
radiation from
PCB, FDTD modeling
of PCB was implemented. Novel FDTD simulation
method
using
multiple-analysis-space was developed
[Kasuga, et al., 2005, 2006a, 2006b].
FDTD modeling
of the common
mode current by a trace placed near
the PCB edge was performed [Tanaka,
et al., 2005]. It is demonstrated
that the common
mode current increases
as the trace
is placed
closer
to the PCB edge and that
a guard
band is effective for suppression
of the common
mode current. These results can serve as design guidelines.
E3-3
Characteristic of EM radiation
at Gigahertz
Frequency and Its Prediction
It has been demonstrated
that a common-mode (CM) current
can dominate
the EMI processes
up to 1GHz, despite
the fact that
a CM current
is smaller
than a differential-mode (DM) current.
Although
the CM current
decreases
above
a few gigahertz,
near and far electric
fields
increase as the frequency
becomes
higher.
It was demonstrated that
the DM component
should
be taken
into account
for EM radiation at gigahertz
frequencies.
[Kayano,
et al., 2005a, 2005b, 2005c, 2005d]
An equivalent circuit model for predicting EM radiation
from a PCB driven
by a connected
feed cable was proposed and demonstrated [Kayano, et al., 2006]. The equivalent circuit model is based on consideration of concepts of CM antenna
impedance
and distributed
constant
circuit
to the conventional
mechanisms
of current-
and voltage-driven.
The proposed
model
can predict
and explain
frequency response of CM current with
engineering
accuracy, and also
express
the intermediate
state
of the current-driven
and the voltage-driven.
E3-4
EM Radiation from
a PCB with Plural Signal
Traces
To provide basic considerations for the realization
of methods
for predicting
the EM radiation from
a PCB with plural signal
traces
driven
in the even-mode,
the characteristics of the EM radiation
resulting
from two signal
traces
on a PCB are investigated
experimentally
and by numerical
modeling
[Kayano,
et al., 2005, 2006]. The frequency responses in the two signal
trace
case can be identified
using
insights
gained
from the single trace case.
Although
crosstalk ensues, the rule
for PCB design
is to keep two high-speed traces on the interior
of the PCB whenever possible,
from the point of view
of EM radiation. An empirical
formula
to quantify
the relationship between the positions of two traces and CM current is provided
and discussed
by comparing
four different
models.
Results
calculated with the empirical formula and
FDTD modeling
are in good agreement, which
indicates
the empirical
formula
may be useful
for developing
EMI design
guidelines.
E3-5 EM Radiation
from Interconnected PCBs
To understand
the electromagnetic
(EM) radiation from
interconnected
PCBs by a cable,
the characteristics of the EM interference
of test model PCB are investigated by experiment
and numerical
modeling
[Kayano,
et al., 2007a, 2007b]. Comparing the cases with and without the interconnection, the ground plane of the interconnected PCBs and the interconnection cable are dominant
radiation factor
in the lower
frequencies.
These
factors
construct
large common-mode antenna. On the other hand, the total
EM radiation at GHz frequencies is simply
determined by the differential-mode current
on the signal
trace,
and cross-talk current
on the victim
traces.
The DM current
on the signal
trace
can be predicted
by transmission
line theory.
E3-6
EMI Simulation
and EMC design
of PCB
Problems to control
electromagnetic
noise
radiated
from digital electronic
devices
have been
pursued in the groups of Koga,
Inoue, Kami, Kuwabara, Schibuya,
and some other. A concise electromagnetic
model
of the power-bus
in a multi-layer PCB has been developed
utilizing
a cavity-mode
model
together with
the segmentation method.
Practical
speed
was enhanced
by 400 times
than traditional
methods,
which is useful as a powerful
tool in designing
PCBs in terms of turn-around time and scale
of computation. Models of electric
and magnetic
coupling on gaped
power
bus structures
and effects of via inductance on split power/ground planes were
also investigated. A method
to evaluate
common-mode excitation on PCBs was demonstrated with
practical
PCBs having
guard
traces.
The evaluation model is called
gimbalance
difference modelh. Accuracy
of the models
has been experimentally
examined.
(1) TDR analysis of EM radiation
from a bend
Discontinuity such
as a bend in a micro-strip line
is known
as one of major
radiation sources. The total radiation
from the micro-strip line
is, however,
being
generally
investigated because
of the difficulties in identifying the radiation
from some
specific
location.
In this study, paying
attention
to the feature
of TDR (Time-Domain Reflectometry)
measurement, an attempt has been
made to extract
the radiation only
from the bend
in a micro-strip line. Such an approach
is useful
in understanding
its radiation mechanism.
As a result,
it has been founded
that the larger
the bend angle is, the larger
the radiation power becomes. The radiation
power
achieved
3.5% at maximum
when the bending
angle
was 90^o at the frequencies below
1 GHz. (J. Wang and O. Fujiwara, 2005)
(2) Coupling
Mechansim
of Digital
IC
The radiated
susceptibility
of a microstrip line with a digital
IC has been investigated. A circuit approach
was used by converting external
incident
electric
and magnetic
fields
into equivalent current and voltage
sources,
respectively,
and the interference voltages
induced
at IC pins were
simulated
by using
a circuit
simulator.
As a result,
it has been found
that the digital IC exhibits a higher susceptibility
for the magnetic
field coupling
compared
to the electric
field coupling
(J. Wang and K. Kuwabara, 2007).
Resonance in
the power-ground plane of PCB is
the prime
concern
when the EM noise is discussed.
A novel
method
to quickly
calculate the effect
in terms of transfer
impedances
between
separated ports/vias[Wang, et al., 2004, 2005a]. Which
was further
extended
for gapped power bus[Wang
et al. 2005b]. Triangular profile of PCB
has become
possible to treat by it[Wang
et al, 206]
E3-7
Modeling
of EMC characteristics of digital IC/LSI
The objectives
of the EMC modeling
of digital
circuits
are extended
to LSIs as noise
driving sources, and linear
macro-models of LSIs,
called LECCS
models,
have been
developed
in Prof. Kogafs
group.
Simulation
performance of a model for core
logic circuits, LECCS-core, and a model for drivers,
LECCS-I/O,. The LECCS-core model
is quite
similar to the model ICEM
which was proposed by French research
group,
and collaboration
to establish
an unified standard
model
for EMC simulation
has been started.@The field of research
is going
into the inside of LSI to estimate the noise current which
drives
PCB. Increase
of frequency range requires this
change.
E3-8 Suppression
of EM radiation
In order to suppress
the undesired electromagnetic
radiation from
a PCB, new PCB structure and shielding
technique are investigated with
FDTD modeling
and experimentally
[Kayano,
et al., 2005; Tanaka, et al., 2006]. A guard-band structure as a method
for suppressing
the EM radiation from
a PCB was proposed
and demonstrated. A signal
trace
is located
between
two ground
traces
(guard-band: GB). The shield
structure
is effective
for suppressing
the CM current
at lower
frequency. However, structures
in which a conductive
plate
exists near
the signal
trace
yield resonances
with high
level peak of CM current on near
and far-field. On the other hand, the guard-band structure is more effective
than other structures
for suppressing
the EM radiation in the considered
frequency range. Therefore
the guard-band will be effective for high-density
PCB packaging
with high-speed traces.
Confinement of EM noise inside PCB is intended
by applying
the periodic
structures
in the power
and ground
plane,
which realizes the band-gap
as appears
in a crystal.
Toyota[2006]
has proven
its effect.
E. 4
EMC problem
related
telecommunication system
The studies of telecommunication system using UTP cables, evaluation
method
of telecommunication system using APD (Amplitude Probability
Density),
interference caused by microwave oven,
EMC evaluation method
of UWB system,
EMC problems
caused
by PLC, interference from PCs having
dithered
clock
systems,
disturbance for the radio system in LF band,
etc, have been
performed
in this period.
Detail
descriptions
are presented
below.
E. 4 EMC problem related
telecommunication system
E4-1 APD measurement
Measuring
the amplitude
probability
distribution (APD) of a disturbance has been
shown
to be a promising method
of defining emission
limits
for protecting
digital
wireless services. The correlation of disturbance APD to the bit error probability
(BEP) of disturbed
wireless systems was demonstrated theoretically
and experimentally
for modulating
schemes
including spread spectrum
[Gotoh, et al., 2005a]. The theory
was extended
for evaluating
the BEP of coded OFDM systems by introducing
multichannel
APD measurement [Gotoh,
et al., 2007a]. A prototype
system
has been successfully
developed
realizing real-time measurement
of multichannel
APD [Gotoh, et al., 2007b]. Theoretical
investigation was made
on the method
and conditions for converting a disturbance APD measured
at one frequency to be valid for another
frequency [Matsumoto,
et al., 2007b]. Application
of APD measurement was proposed to the CISPR compliance test
of radiated
disturbances from
microwave ovens
[Gotoh,et al., 2005b]. A method
was proposed
for evaluating
the accuracies
of APD measuring
instruments [Gotoh,
et al., 2006].
E4-2
Interference caused by microwave oven
noises
Leakage of
EM waves
from microwave ovens
may cause
unwanted
interference to wireless
LAN systems
using
the 2.4-GHz band. An FM-AM model of oven noise
has been developed,
and employed
to evaluate
degradation in the transmission quality of
DS-SS (direct
sequence spread spectrum)
WLAN (wireless LAN) systems interfered
with the oven
noises
[Matsumoto,
et al., 2005a]. Band-limited
characteristics of oven
noise
were discussed
[Matsumoto,
et al., 2005b], and the results
were applied to develop a new reduction
method
of oven interference
in DS-SS WLAN systems
by means
of adaptive
filters
[Matsumoto,
et al., 2005c].
E4-3
UWB (Ultra wide-Band) systems
In order to evaluate
peak radiating power
from a UWB (ultra
wideband) device accurately,
a waveform reconstruction method
of the electric
field emitted
by a UWB device
was developed
based
on the time-domain measurement by introducing
a compensation technique of waveform
distortions
caused
by the receiving antenna
[Ishigami,
et al., 2005a]. A measurement
system
was developed
for monitoring
electromagnetic
field distribution in the UWB frequency
band [Ishigami, et al., 2006]. A new method
has been proposed and demonstrated for evaluating the interference
between
the UWB and the wireless LAN by using the GTEM cell
[Yamada,
et al., 2007].
E4-4
Interference from PCs employing spread spectrum
clock
systems
Recent electronic
devices,
such as PCs (personal
Computers),
usually
employ
SSC (Spread
Spectrum
Clock)
techniques to reduce
the peak spectral
amplitude
of their
radiating
clock
harmonics by modulating the clock frequency.
Measurement was conducted for investigating two-dimensional
distribution of frequency
modulated
noise
current
on a PC chassis
[Marubashi, et al., 2006]. Investigations were
made on the effect
of the modulating
parameters
of SSC on the reduction
in spectral
amplitude
of clock
harmonics [Matsumoto,
et al., 2005d, 2005e, 2006a]. The impact of frequency
modulated
harmonics on wireless
systems
was analyzed
for Bluetooth
[Murakami,
et al., 2005, 2006a], MB-OFDM UWB [Murakami, et al., 2006b, 2006c], and OFDM based WLAN [Shimizu,
et al., 2005], [Matsumoto, et al.,
2006b, 2007a]. It was found that frequency modulated clock harmonics
in many cases
degraded
the transmission
performance of such
wireless systems more
significantly in comparison with
unmodulated
ones.
E4-5
EMC problem
related
PLC (Power
Line Communication)
system
The increase
speed
of power
line communications
may affect existing wireless
communication
system
mainly
in HF band. To cope
with this
problem,
the effect of buildings on the attenuation in the electric
field was investigated by numerical
calculation assuming a model of indoor PLC system and typical
structures
and materials
used for buildings in Japan
[Ishigami,
et al., 2007].
E4-7
Investigation of disturbance for LF band
The Japan Standard
Time signal
is transmitted
at the frequency of 40 kHz and 60 kHz. Electromagnetic
disturbances were
measured
and their
statistical
properties
were investigated in the frequency
band [Iwama, et al., 2006, 2007].
E. 5
EMC test facilities
The studies of test methods using rotating electromagnetic
fields,
correlation between GTEM cells
and anechoic
chambers,
evaluation methods
of reverberation
chamber,
etc, have been
performed
in this period.
Detail
descriptions
are presented
below.
E5-1 Immunity/susceptibility
test method
In order to clarify immunity/susceptibility characteristics against
radio-frequency
electromagnetic
fields,
a new test method
of using
electromagnetic
fields
two-dimensionally
rotating
at a very low rate
was proposed
by Prof. Kamifs
group,
which demonstrated the characteristics depicted in visualized
three-dimensional map. They also applied the method
to a four-septum TEM cell.
E5-2
GTEM Cell
A GTEM (gigahertz transverse electromagnetic)
cell is used
for immunity
and emission
tests. The correlation between the immunity-test
result
in a GTEM cell and that
in an anechoic
chamber
was examined
theoretically
[Ishigami,
et al., 2001, 2003b]. The average
electric
fields
of the EUT surfaces
in a GTEM cell and an anechoic
chamber
were calculated
using
the FD-TD method
in order to evaluate a suitable
installation and size
of EUT in the GTEM cell. When the size
of EUT was 10%, 20%, or 30% of the septum
height,
the difference in both
the test result of the GTEM cell and the anechoic
chamber
was expected
to be about
1dB, 2dB, or 2-3dB, respectively.
Moreover, when
the EUT surface
approached
the septum
and floor conductor,
the difference increased.
E5-3
Reverberation
chamber
Statistical properties of
the transmission
characteristics in a reverberation
chamber
were analyzed theoretically
and experimentally
[Harima,
2005b]. The results
were applied to developing
a new technique to measure the radiating power
of wireless devices in a reverberation
chamber
[Sugiyama,
et al., 2005], [Harima, et al.,
2005c].
E.6 ESD and system level
EMC
The studies of evaluation
method
of system
level EMC, geospace environment
simulator,
meta -material
type RF absorber,
etc, have been
performed
in this period.
Detail
descriptions
are presented
below.
E6-1 ESD measurement
The studies on human electrostatic
discharges
(ESDs) and ESD generators simulating the human
ESD, which is being used
for standard
immunity
testing
prescribed by the International Electro-technical
Commission (IEC), have
been conducted in this
period
by Prof. Fujiwarafs group.
Detail
descriptions
are presented
below.
(1) Measurement of discharge
currents
from human ESDs
Discharge currents through a hand-held metal piece from a charged human body were measured
with respect to approaching
speeds
and charge
voltages.
A circuit
approach
for calculating
the discharge
current
has also been
given.
As a result,
it was shown
that in case
of 300 V charge
voltage,
the current
waveform is not affected by the metal piece approaching
speed,
while in case
of 800 V charge
voltage,
the fast approach
gives the higher current peak.
These
current
waveforms can be predicted from
the time invariant spark resistance and the measured
frequency characteristics of human body
impedance
seen from
a hand-held
metal
piece
[Taka, et al., 2005].
A method
was presented
for estimating
the voltage
waveform of a spark from
the measured
discharge
current
through
a hand-held
metal
piece
from a charged
human
body, which
exhibited
the presence
of arcs following
the spark.
In view of the arc and a time-varying resistance based on a spark resistance formula, an improved
circuit
model
was given
in order to calculate
the discharge
current
in relation
to the charge
voltage
of a human
body [Mori,
et al., 2005a].
ESD events due to metal objects electrified
with low voltages
give a fatal
electromagnetic
interference to high-tech information equipment. In order
to elucidate
the mechanism,
with a 6-GHz digital oscilloscope,
the spark
current
was measured
through
a hand-held
metal
piece
from a charged
human
body, and proposed a current calculation
model.
Taka, et al. investigated the properties of a spark discharge
itself
through
a hand-held
metal
piece
from a human body
electrified
with low voltage
below
1000 V. From
the measured
discharge
current
waveform and the gap voltage
calculated from the above-mentioned
current
calculation model, the gap resistance with
respect
to time was derived,
and the gap length
was estimated
using
a spark
resistance formula. As a result, it was shown that
for the charge
voltage
from 200 V to 1000
V, the gap length
approximately increases
with the charge voltage,
while the corresponding
gap breakdown field
is almost
kept constant.
The findings
were supported by the experimental
results
that other researchers
obtained
with their different
set-ups consisting
of metal
electrodes
[Taka, et al., 2006a].
The discharge
currents
due to air discharge
through
a hand-held
metal
piece
from a charged
human-body with respect to charge voltages
below
1000 V were
measured.
The gap breakdown fields were
thereby
estimated,
which were
validated
from the Paschenfs
law and other
researcherfs
experimental result [Taka, et al., 2006b].
A method
was presented
for deriving
a gap breakdown field
from the measured
discharge
current
due to collision
of a hand-held
metal
piece
from a charged
human
body. Measurements of the discharge
currents
were made
for charge
voltages
from 200 V to 1000
V. The corresponding
gap breakdown fields were
derived,
which were
validated
in comparison with
an empirical
formula
based
on the Paschenfs
law together with
other
researcherfs
experimental results [Taka, et al., 2006c].
In IEC 61000-4-2 for electrostatic
discharge
(ESD) immunity
testing,
an ESD-gun is used to simulate
the ESD events
from a charged
human
body. The gun of this
kind injects
into a device under test
the discharge
current
through
a lumped resistor
from a charged
lumped capacitor.
In actual
ESD events
from charged
human
bodies, however, the charge distributed on the body surface
is discharged
through
a spark
from the fingertip,
and its situation is essentially
different
from that
of the ESD-gun. To understand the behavior of the
above-mentioned
discharge
current,
with a 6GHz digital oscilloscope,
the discharge
current
was measured
through
a hand-held
metal
piece
from a charged
human
body, and proposed an equivalent circuit model for calculating
the discharge
current
with a time
invariant
spark
resistance. Furthermore, with
respect
to the approaching
speed
of the hand-held
metal
piece,
the discharge
currents
were measured
through
a metal
piece
from a human-body
with a charge voltage
raging
from 200V to 1000V,
and estimated
the resultant
voltage
waveforms from
the above-mentioned
equivalent circuit model. Through these results, in conjunction
with the metal piece speed, the dependence on the charge voltage
of current
peak, current rise
time, time-varying spark
resistance, spark length and breakdown field
was shown.
It was confirmed
also that
the spark
resistance value
at the current
peak time
enables
one to calculate the discharge
current,
which supports the validity
of the previously proposed circuit model [Mori, et al., 2006a].
It has widely been accepted that ESD events
due to charged
human
bodies with
low charge
voltages
below
1000 V cause a fatal
electromagnetic
malfunction
in high-tech
information equipment. In order
to understand
a mechanism
of such human ESD events, with
a 12-GHz digital
oscilloscope,
discharge
currents
were measured
through
a hand-held
metal
bar or a fingertip
with an aluminum
foil attachment from
a charged
human
body with
a charge
voltage
of 600V, and the effect of the aluminum
foil size
on discharges
through
a fingertip
was examined.
In addition,
by using
an equivalent circuit previously
proposed
for calculating
the discharge
currents,
the corresponding
discharge
voltages,
measurement of which
is basically
impossible, were
estimated.
As a result,
it was shown
that the hand-held metal
bar and aluminum
foil attachment produce a one-shot
discharge
current
with steeply rising time
shorter
than a hundred picoseconds
and the corresponding
discharge
voltage
abruptly
changing
from the charge voltage
to certain
remaining
voltages
due to arcs following
sparks,
and the peaks of discharge
currents
through
a fingertip
increase with
the attachment foil
size. This
suggests
that the growth of a spark can be affected mainly by the amount of charges accumulated in the stray capacitances
around
the fingertip.
For the discharge
through
a fingertip
without
any aluminum
foil attachments, however, the measurement shows
that the fingertip
produces
multiple-shot discharge currents with gently
rising
time larger
than a hundred picoseconds
and significantly low amplitudes, which are entirely different
from the above cases.
This means that
the fingertip
only could not provide electric
energy
enough
for a spark
to grow [Taka,
et al., 2007a].
With a
12-GHz digital
oscilloscope,
discharge
currents
were measured
through
a fingertip
or a hand-held
metal
bar from a charged
human
body with
a charge
voltage
of 600V, and comparison of their discharge
waveforms was made
in conjunction with the corresponding
discharge
voltages,
which were
derived
from our previously
proposed
equivalent circuit model [Taka,
et al., 2007b].
A transfer
impedance
of an SMA receptacle
as a wideband measurement electrode
being
used for discharge
currents
from a charged
human
was derived,
and its frequency characteristics were
measured
from 300 kHz to 20 GHz. With a 12-GHz digital oscilloscope,
measurement of discharge
currents
through
a hand-held
metal
bar from a charged
human
was also made,
and thereby
the injected
currents
on the SMA receptacle
were reconstructed from
the measured
transfer
impedance
[Kagawa, et al., 2007].
(2) Characteristic measurement of discharge
currents
from ESD generators
An immunity testing method
for ESDs is being
specified
in IEC 61000-4-2, in which the contact discharge
of an ESD-gun is being
normally
specified.
Air discharge
testing
is known
to be a severe
immunity
test compared
to the contact
discharge
testing,
while the discharge
current
injected
is not well reproduced. Grasping
the behavior
of the current
injected
by the air discharge
would be helpful in establishing
the worst-case
ESD immunity
testing.
Mori, et al. previously
measured
the discharge
currents
for air discharge
testing
onto the IEC recommended
current
transducer with a commercially
available ESD-gun, and showed
that there exists
a specific
relationship of Ip·trΔ/VC=constant
(Δ=0.75), between
rise time tr and current peak
Ip. The current transducer, however, has frequency
dependent
transfer
impedance,
which should affect
the measured
current
waveform. Mori,
et al. investigated if the above-mentioned
specific
relationship can be obtained for air discharge
of an ESD-gun onto a ground assumed for a metal enclosure
of electronic
equipment under test.
A method
was presented
for estimating
the discharge
current
from simultaneously
measured
magnetic
fields
with two magnetic
field probes regardless of the distance
between
the gun discharge-point and the probe position, which was validated for contact
discharge
of an ESD-gun to a SMA connector. With this method,
the discharge
currents
injected
onto a ground for air discharge
testing
of an ESD-gun with intentionally
fast and slow
approaches
were estimated. As a result, it was confirmed
that there is a specific
relationship between rise
time tr
and current
peak Ip
of Ip·trΔ/VC=constant
with Δ=0.57 independent
of charge
voltages
and gun approaches
[Mori, et al., 2005b].
ESD testing is prescribed
in the IEC 61000-4-2, which is conducted
by injecting the transient current through contact
/air discharge
of an ESD-gun. The current
calibration in the IEC standard,
however,
is being
made for the contact
discharge
because
the current
waveform injected through the air discharge
is greatly
affected
by a gun approaching
speed.
With two kinds
of commercially
available ESD-guns, therefore,
the transient
currents
were measured
for the air discharge gun with arbitrary approaching
speeds.
As a result,
it was shown
that a similar
specific
relationship holds
between
the rise-time
and current
peak for each
ESD-gun despite
the poor reproducibility
of the current
waveform, which
is also supported by other researcher's
finding
for the air discharge of a charged
metal
spheroid
[Mori, et al., 2005c].
By testing discharge
current
of ESD guns on both discharged
at contact
and in air, their
relationship was examined between current peak/rising time and charging voltage.
As a result,
it was found that
the discharge
in air had little effect
on the discharge
current
of approaching
speed
at less than
1 kV, and that it had higher peak and shorter rising time than those of the contact
discharge
[Mori, et al., 2005d].
According to
the IEC 61000-4-2 for ESD immunity testing, an
ESD-gun with charge voltages
above
2 kV is used to inject
a discharge
current
onto a device under test.
The current
waveform is prescribed
in the IEC standard
for contact
discharge,
but is not specified
for air discharge
due to its poor reproducibility,
although
the air discharge
gives a severe
immunity
testing.
Furthermore, it is well
known
that ESD events with
low charge
voltages
below
1 kV cause
serious
failure
to high-tech
equipment, while
its mechanism
remains
unknown.
In order to clarify the severity
of low voltage
ESD events,
using
a 12-GHz digital
oscilloscope,
current
waveforms through air discharge
of the ESD-gun with charge voltages
from 200V to 1 kV were
measured.
As a result,
it was shown
that the current peak
and rise time
become
higher
and shorter,
respectively,
in comparison with
those
for contact
discharge,
whose
tendency
was almost
the same as the results for charge voltages
below
1 kV previously obtained with a 6-GHz digital oscilloscope.
It was also shown that
the rise time
measured
for charge
voltages
below
500 V reaches
the limit
of measurement (35 ps) [Mori,
et al., 2006b].
By using a 12-GHz digital oscilloscope,
discharge
currents
were measured
for air discharge
of an ESD-gun with charge voltages
below
1 kV, and demonstrated that
the rise time
reached
the limit
of measurement. Based on the Gaussian response of the oscilloscope,
the rise time
limit
was investigated [Mori,
et al., 2006c].
Measurements were made in
the frequency range from
300kHz to 6GHz of the transfer impedance of a commercially
available calibration
target
used for the immunity testing against
ESDs that the IEC prescribes,
and thereby
the waveforms of discharge
currents
injected
onto the target were
reconstructed from
their
observed
output voltages
for contact
and air discharges
of an ESD generator
with a charge voltage
of 2kV. As a result,
it was confirmed
that the transfer
impedance
has an absolute
value of almost 1 Ά at frequencies up to 6 GHz, while
resonance
phenomena
were observed
at frequencies
around
2 and 5 GHz. This result has demonstrated that
the reconstructed discharge
current
waveforms agree well
with those of the observed
voltages
for the contact
discharge
and air discharge
with slow
approach,
producing the current with
a rise time
of almost
1 ns, while the reconstructed current has a slightly
small
peak and gentle rising part
in comparison with
those
of the observed
voltage
for the air discharge with fast approach,
which gives
the current
within
a rapid rise
time of a hundred pico-seconds [Taka, et al., 2007c].
E6-2 Equivalent circuit model for human ESD
A circuit approach
for calculating
the discharge
current
through
a hand-held
metal
piece
from a charged
human
body has been
proposed
by Prof. Fujiwarafs group.
It has been demonstrated that
the current
waveforms can be predicted from
the time variant
spark
resistance and measured
frequency characteristics of the human body
impedance
[Fujiwara,
et al., 2001a, 2003a].
E6-3 ESD contact
ad air discharge
measurement
Measurement was made
by Prof. Fujiwarafs group
for the discharge
currents
injected
onto the Pellegrini
target
for the contact
air discharge
of a commercially
available ESD-gun with
respect
to its approaching
speed
to the target.
It was found that
the fast approach
of the ESD gun provides
a sharp
current
with a steeper rise-time and a higher peak,
while the slow
approach
gives a gentle current with
the shorter
rise-time
but lower
peak compared
to the case for the contact
discharge.
It was also found
that there exists
a specific
relationship between the rise-time and the peak
current
normalized
to the charge
voltage
regardless of the approaching
speed
of the ESD gun [Fujiwara,
et al., 2001b, Fujiwara,
et al., 2004].
E6-4 FDTD simulation
of contact
discharge
by an ESD-Gun
The electromagnetic
noise
caused
by an electrostatic
discharge
(ESD) is a major
source
of malfunction
to high-tech
equipment. The ESD testing, therefore,
is being
specified
in the IEC61000-4-2, which prescribes the current waveform
from an ESD gun through a IEC recommended
current
detector
(Pellegrini calibration
target).
This IEC current waveform,
however,
does not always correspond
to the one injected
onto an actual device for ESD testing. Prof.
Fujiwarafs
group
simulated
a contact
discharge
to ground
plates
using
our previously developed
FDTD model
of an ESD gun. The induced
voltages
through
a magnetic
field probe were
simulated
when the discharge
current
was injected
directly
to the ground
plate
in contact
with an ESD gun, whose results were
confirmed
with respect to the ground plate sizes
experimentally
[Fujiwara,
et al., 2002, 2003b].
E6-5 Safety evaluation
for stochastically varying
electromagnetic
fields
The cumulative
amplitude
probability
distributions (APD) of leaked electric
fields
in fusion
experimental facilities were measured
and an approach
to derive
their
time-average from
the measured
APD was proposed
[Wang, et.al., 2004]. The statistically
averaged
electric
field showed
fair agreement with
the time-averaged electric
field during 6 minutes being specified
in the safety
guidelines. This
finding
suggested
the usefulness of the APD measurement in lieu
of the field measurement during a 6-minute
period
because
the APD can be obtained
for a time period
much less
than 6 minutes.
E6-6
Geospace
environment simulator
In order to make quantitative
evaluation of electromagnetic
environment around spacecraft,
three
dimensional electromagnetic
particle
simulations
are being
performed
using
125 nodes (2 TB Memory) of the Earth
Simulator
System,
reporting
various
physical
processes
induced
by emission
of heavy ions in electric
propulsion.
E6-7 Application
of meta-material
to EM wave absorber
and shielding
material
Meta-material
is the material
which can control
the dielectric constant
and the magnetic
permeability.
At the special
condition, the real
part of the dielectric
constant
and the magnetic
permeability
are negative.
This phenomenon makes
the flexibility of a design for EM-absorber
and shielding
material.
Metamaterial–based EM wave absorbers have been proposed and developed
for the use of EMC applications. A new concept
of gEquivalent Transformation Methods
of Material
Constanth
(ETMMC) [Kotsuka
et al. 2004,2005,2006a,2006b] has been proposed, and
g EM-wave absorber
based
on Integrated
Circuit
Concepth
[Kawamura
2006, Kotsuka
2006c] have
been developed. In
the course
of these
researches,
new metamaterial
EM-wave absorbers
have has been
proposed.
These
metamatrial EM-wave
absorbers
are based
on the concept
of gautonomous control
system
of living cellh
(ACMM) which can change
the material
constants
by computer
control
[Kotsuka
et al. 2006d, 2007a,2007b].
Natural EM Noise
E.7 Lightning
Study in Prof. Kawasakifs groupiThis section is carried
over from
the former
reportj
Thunderstorms observed
by TRMM/PR and LIS have been investigated,
and Lightning
Research
Group
of Osaka University (LRGOU) has unveiled
several
interesting
features.
Correlation between lightning activities and the snow
depth
of convective
clouds
may follow
the power-five law. The power five
law means
that the flash density is a function
of the snow-depth to power five.
The definition of snow
depth
is the height
of detectable cloud tops
by TRMM/PR from the climatological
freezing level,
and it may be equivalent
to the length
of the portion
where
the solid
phase
precipitation particles
exist. This
is given
by examining more
than one million
convective
clouds,
and we conclude that
the power
five law should be universal from
the aspect
of the statistic.
Three thunderstorm
active
areas are well
known
as gThree
World Chimneysh,
and those
are the Central
Africa,
Amazon
of the South America, and South East Asia. Thunderstorm
activities
in these
areas are expected to contribute
to the distribution of thermal
energy
around
the equator
to middle latitude
regions.
Moreover thunderstorm
activity
in the tropical
region
is believed
to be related
with the average temperature of our planet
earth. That
is why long term
monitoring
of lightning
activity
is required.
After
launching TRMM we have
accumulated seven-year
LIS observations, and statistics
for three
world chimneys
are obtained.
We have recognized
the additional
lightning
active
area, and that
is around
the Maracaibo
lake in Venezuera.
We conclude that
this is because
of geographical
features
of the Maracaibo
lake and the continuous
easterly
trade
wind.
Lightning Activity during El Nino
period
is another
interesting
subject.
LRGOU studies thunderstorm
occurrences over
west Indonesia
and south China,
and investigates the influence
of El Nino on lightning . We compare
the statistics
between
El Nino and non El Nino
periods.
We learn
that the lightning activity during El Nino
period
is higher
than non El Nino
period
instead
of less precipitation
on the ground
during
El Nino period.
Since
we expect
the strong
correlation between precipitation
and lightning
activity,
the results
seem to be against
the conventional
common
sense.
However
analyzed
results
for these
two areas show
no contradictions, or we can
say that the results are exactly same
from the aspect
of statistics.
The meteorological
comprehension
is still
remained.
Lightning Research
Group
of Osaka University (LRGOU) has been working for a novel technique of VHF Broadband Digital Interferometer
(BDITF) to monitor
thunderstorm
activity
and to image
lightning
channels
for these
ten years. The VHF BDITF has been improved
to be a quasi operating system, and LRGOU has equipped
the BDITF in Korea, in Australia
and at four sites near
central
Japan.
LRGOU controls
these
BDITFs through
internet,
and conducts
remote
and continuous
monitoring
of lightning
activity.
The BDITF antenna is capacitive,
which bandwidth
is from 25 to 100 MHz including
amplifier, and its shape
is circular with
about
30 cm diameter.
The BDITF consists
of three
antennas,
and these
antennas
are deployed
at three
apexes of an isosceles right
triangle.
The length
of two sides around the right
angle
is between
5 to 10 meters,
because
the antenna
spacing
is not necessary
to be fixed to some
required
length.
These
two sides are normally
set up to direct
to north-to-south and east-to-west. Once we have a lightning
flash,
a few thousands of VHF impulses
are emitted, and the BDITF can detect VHF impulses
within
about
50 km. The scheme to estimate source location of VHF
impulses
is based
on the Fourier
analysis.
Received
VHF impulses
are decomposed into Fourier
components
by FFT (Fast Fourier Transform).
Phase
differences for all Fourier components
between
two antennas
output are calculated
to estimate
the incident
angles
against
the base line
of two antennas.
Since
one unit of BDITF consists of three antennas,
two dimensional source locations, azimuth and elevation,
can be observed.
If we install
two sets of BDITF with
proper
spacing,
we are able to have
3-D image
of lightning
channels.
BDITF observations during winter thunderstorm
seasons
have been
carried
out around
Mikuni
and Kanazawa.
Three
dimensional images of lightning progressions
are observed
around
Mikuni.
The propagation velocity of the negative breakdown is estimated, and it is in the order of ten to power five
meters
per second.
This value
is nearly
the same of the velocity formally
observed
by the optical
streak camera. The lightning channels with
branching
are captured,
and we learn
the excellent capability
of BDITF. Possible positively
charged
region
is visualized
by detecting negative breakdown during continuing
current.
The observations around Kanazawa
for winter
thunderstorms
are still
ongoing.
An electric
filed change
and VHF/UHF radiation associated
with positive cloud-to-ground (CG) flashes during winter in Japan
has been observed,
and it can be noticed
that the intensity
of VHF/UHF radiation increases
immediately
after
a return
stroke
occurrence. It is well
known
that VHF/UHF radiation
intensity
by a negative
CG decreases
during
and after
a return
stroke,
and the strong
VHF/UHF emission
after
the return
stroke
is believed
be peculiar
to the positive
CG. VHF/UHF radiation due to negative CG flashes is emitted
from a tip of leader
progression,
and a lightning
channel
imaging
is available by VHF/UHF interferometer
observations. In case
of a positive
CG, channel
imaging
of a VHF/UHF interferometer
is not available. To interpret
the discrepancy of VHF/UHF source mapping
between
negative
and positive
CGs, a theory
of gBi-directional
Leader
Concepth
is introduced.
That means VHF/UHF radiation
associated
with a negative breakdown can be observed
for both positive and negative CG, and for a negative CG that is the leader
progression
tip, and for positive
CG that is possible
positive
charge
regions.
From this
aspect,
the location
of VHF/UHF radiation source for positive CG mapped by interferometers
may be equivalent to the location of positive charge distribution inside thunderclouds.
In other
words we are able
to see the charge
distribution by the interferometer.
The 3D mapping
for positive
CG obtained
during
winter
thunderstorm
in Japan
by means
of VHF/UHF interferometer
frequently
gives a very
large volume
of source
distribution, and its horizontal
extension
occasionally
exceeds ten kilometers.
The most possible
altitude of the distribution of VHF/UHF source location is equivalent to or slightly
lower
than the altitude
of -10 degree
Celsius.
The sources
are superimposed on the radar cross section, and it
is noticed
that sources are rather
located
in a stratified
region
instead
of a convective
region.
Though
it has been believed
that the thundercloud
during
winter
in Japan
might be small size
because
of weak convection,
our observations by VHF/UHF interferometer
are against
the conventional
understanding.
We have occasionally
experienced the MCS like thunderclouds even in winter.
The total
amount
of charge
is estimated
to be a few hundred
Coulombs,
and it is supposed
that thunderclouds,
which cause positive CG during winter in Japan, should be a possible
parent
thundercloud.@
E.8 Lightning and spherics
Ionospheric Alfven Resonances
(IARs) as a kind of resonance
phenomenon in the ionosphere
and mangetosphere,
were observed
in Kamchaktka, Russia
(L = 2.1) by Hayakawa et al. [2004], who have reported
its statistical
results
on the spectral
resonance
structures
in the ULF /ELF range
from 0.1 to 5.0 Hz on the basis of the long-term observation
during
2.5 years. Then,
Surkov et al. [2006] have presented
a theory
for mid-latitude IARs excitation
due to electromagnetic
waves
radiated
from the lightning discharges,
and have found
that nearby thunderstorms
in a range
of 1000 - 2000 km make
a main contribution
to IARs. The intensity of Schumann
resonance,
the global
electromagnetic
oscilliations,
was monitored
at Moshiri, Japan
and a good correlation was found
between
the global
ground
temperature and the Schumann
resonance
intensity
[Sekiguchi
et al., 2006]. Ionospheric
DC electric
fields
and plasma
density
variations
associated
meteorological
phenomena
such as tropical
storm
and typhoon
were investigated [Sorokin et al., 2005].
ELF wave phenomena
in the Earth-ionosphere
cavity, known as Schumann
resonance,
have been
studied
in order to monitor the lower ionosphere
and global
lightning
activity.
Ando et al. 2005a] have
developed
an algorithm
to deduce
the global
lightning
activity
map as an inverse problem to the
ELF data observed
at a few stations
in the world. Anomalous
Schumann
resonance
effects have
been found
for earthquakes by Hayakawa
et al. [2005a], who have found an anomaly
in Schumann
resonance
(e.g., enhancement in the fourth harmonic
etc.) in Japan,
in possible association with
a large earthquakes
in Taiwan.
They have
interpreted
that this
anomaly
is due to the interference
between
the direct
signal
from a major lightning source in America
and the signal
scattered
from the Seismo-ionospheric
perturbation over
Taiwan.
Nickolaenko and Hayakawa [2007] have
reviewed
the latest
works
on Schumann
resonances
and related
ELF transient
events
during
the last several
years, including
ionospheric
non-uniformities, the use as a global thermometer,
new objects for studies,
and new results
in old problems.
Nickolaenko et al. [2004] have
developed
a computer
algorithm
for accelerating the convergence
of the time series
computations of the ELF pulsed
waveforms propagated
in the Earth-ionosphere
waveguide.
E.9
Electromagnetic
phenomena
associated
with earthquakes
Seismogenic ULF
emissions
were detected
prior
to some large
earthquakes ; for example, 2004 Niigata-Chuetsu earthquake
[Ohta et al., 2005; Hayakawa et al., 2006a] and 2004 Indonesia
Sumatra
earthquake [Ohta et al., 2007]. Ohta et al.
[2005] performed
the direction
finding
from Nakatsugawa,
Japan
and found that
the observed
azimuthal
directions
are consistent
with the epicentral directions
of both earthquakes,
giving a strong
evidence
on the precursory ULF emissions.
Some sophisticated
signal
processings
were developed
and utilized
to detect any weak
seismogenic ULF emissions
[Serita et al., 2005; Hattori et al.,
2006; Ida et al., 2006; Ida and Hayakawa, 2006]. Ida et al. [2006] and Ida
and Hayakawa [2006] have
applied
the fractal
(mono- and multi-) analyses
to ground-based ULF data to suggest
that those fractal analysis are very
useful
in examining the nonlinear
process
(self-organized
criticality)
taking
place
in the lithosphere.
Hayakawa et
al. [2007] have reviewed
seismogenic ULF emissions,
starting
from earlier
to the latest
results.
The most important
conclusion from
all ULF events
reported
before,
is that there must
be a threshold
of the possible detection of seismogenic ULF emissions
as functions
of earthquake magnitude and epicentral distantce. Also,
the generation
mechanisms
of ULF emissions
(microfracturing, electro-kinetic
effects etc.) are also
discussed.
Hayakawa
[2007] has reviewed
the subionospheric
VLF/LF propagation during earthquakes,
and have presented
event
and statistical
studies on the correlation of ionospheric
perturbations as seen
by VLF/LF and earthquakes with
large magnitudes, say with
magnitude larger
than 6.0. Also,
a few possible mechanisms
have been
suggested
and discussed.
A precursor
of ionospheric
perturbations to the Sumatra
earthquake was found
in a subionospheric
VLF propagation signal
[Horie
et al., 2007]. Associated
with other large
earthquakes, an anomalous
effect on Schumann
resonance
was detected. For one of those earthquakes,
the anomaly
appeared
one week to a few days
before
the main shock [Hayakawa
et al., 2005], and the anomaly
was numerically
modeled
[Nickolaenko
et al., 2006]. A subionospheric
LF and VLF propagation anomaly
caused
by ionospheric
disturbances [Maekawa et al., 2006; Yamauchi et
al., 2007] and anomalous
sporadic
E layers
were observed
in prior
to earthquakes [Sorokin et al., 2006a]; the effect was numerically
modeled
[Soloviev et al., 2006]. Various
applications
of Schumann
resonance
to ionospheric
studies including
an earthquake effect
were reviewed
[Nickolaenko
and Hayakawa, 2007]. An electrodynamic
model
was developed
for strong
DC electric
field formation
in the ionosphere above earthquake
regions
[Sorokin
et al., 2006].
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